An electronic device is formed with many circuits. Particularly, an electronic device for communication may include a Radio Frequency (RF) circuit for controlling RF, and the RF circuit generally includes a frequency synthesizer that generates a sine wave signal and/or a RF signal. In a partial configuration of the frequency synthesizer, a block that generates a signal of a desired frequency is referred to as a Voltage Control Oscillator (VCO).
An amplitude of an output signal of the VCO may be changed according to a quantity of a consumption current of the VCO. A consumption current of the VCO may be generally changed according to a process deviation and capacitance of the VCO. Therefore, in order to constantly maintain an amplitude magnitude of an output signal of the VCO to a desired value, it is needed to optimize a current. According to a method of controlling a current of a related-art VCO, an output amplitude magnitude of the VCO is compared with a reference voltage, and an analog feedback loop method of adjusting a gate voltage of a transistor that operates with a current source of the VCO according to a comparison result is generally used.
In an analog component, such as an Operational Amplifier (OP-AMP) and a comparator frequently used in the above-described feedback loop method, a gain, an operation speed, and a bandwidth may be easily changed according to a process change. Therefore, when each analog component performs a stable operation in spite of a process change, an output voltage of the VCO may be accurately controlled. Therefore, high design completeness of an analog circuit constituting the feedback loop as well as a design of the VCO is needed.
Further, when using the analog feedback loop, in order to measure an output voltage of the VCO, each analog component should always operate. Thereby, additional current consumption, other than a consumption current of the VCO, increases and thus it is very difficult to optimize a current of the VCO. Further, phase noise of the VCO may be deteriorated by noise generated by the analog components. Further, in analog circuits, when an existing process is changed to a new process, e.g., when a 180 nm Complementary metal-oxide-semiconductor (CMOS) process is changed to a 65 nm CMOS process, a performance is greatly changed and thus a feedback loop appropriate thereto should be again designed.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.